Honestly, I don't consider it a "historic choke". It's utterly disappointing, but I believe Tampa Bay was never meant to be an elite playoff team to begin with. They also got dominated for all 12 periods except for the first one, so it's not like they pulled a 3-0 lead like San Jose and choked all the way down. CBJ was the better team the whole time, hands down.
Also, at this point in the NHL, we should know that regular season games are meaningless. Grit and heart mixed with a good amount of skills is what wins playoff games. The league has way too much parity nowadays to predict the outcome of a series, so when grit and heart comes into play, anyone can win. Sure, a first round sweep against the best team of the league never happened before, but 25+ years ago the difference between the "#1 seed" and the "#8 seed" was massive. It's historic, but at the same time, this scenario can happen only once a year so the odds are low to begin with.
Columbus stacked their team at the deadline with a bunch of players, including Duchene who clearly had something to prove in the playoffs. They also played fantastic hockey at the end of the season. They didn't play like a 8th seed AT ALL. Plus, it wasn't a typical 8th seed, they finished with 98 points on a stacked metro division.
Panarin, Duchene, Dubois, Atkinson, Jones, Werenski, Bobrovsky and tons of good depth players and key veterans. It was a legit good team.
Tampa, on the other hand, regressed a lot by losing Hedman at the end of the season. We're talking about a legit #1D here, not a random #2D. Stamkos and Kucherov are also well known underperformers in the playoffs, so them being invisible wasn't even that surprising.
Another important factor : Powerplays. Stamkos, Kucherov and Point combined for 54 powerplay goals this season. That was part of the team's identity, and a big reason why they finished with that many wins. During this series though, they pretty much had no powerplay opportunities against the second-least punished team of the league.